Corrosion inhibiting additive compositions for fuel oils



United States Patent Office 3,429,673 Patented Feb. 25, 1969 ABSTRACT OF THE DISCLOSURE This invention relates to a corrosion inhibitor composition for fuel oils consisting of a mixture of:

(A) salts of aliphatic carboxylic acids having from 6 to 12 carbon atoms, with alkylamines substituted with hydroxyl groups; and

(B) salts of aliphatic carboxylic acids having from 4 to 12 carbon atoms, with alkylamines having from 4 to 16 carbon atoms, with the proviso that the total number of carbon atoms in said salt is more than said salts being present in said mixture in a ratio of 1:9 to 9:1 parts by weight. The invention also relates to fuel oils containing from 50 to 1000 parts per million of the aforesaid corrosion inhibitor composition.

The prior art The inner walls of the metal containers for the fuel oil supply are, as is well known, exposed to intense corrosion attacks. Primarily, these attacks are caused by water which enters the tank together with the fuel oil or possibly absorbed by the air which is drawn into the tank as the fuel oil is used. In any event this water tends to collect as a coherent layer on the bottom of the supply tank and as condensed moisture on the walls of this tank above the fuel oil level. Due to the fact that the oxygen present in this water is replenished continuously from the fuel oil during corrosion, this corrosion is advanced to a still greater degree. A further intensification of these corrosion attacks is caused by salts dissolved in the water, primarily chlorides, which get into the fuel oils in transportation and pass to the aqueous phase. The presence of salt-containing ground waters is even more dangerous, as they do not allow the presently known corrosion inhibiting agents, possibly present in the fuel oil, to take effect. Therefore, for some time, most types of fuel oils have been admixed with additives which are supposed to reduce the corrosive attacks.

As corrosion inhibitors organic nitrogen compounds, such as amines, have already been suggested, in particular long chain amines as well as alkanolamines, amides and their salts, also fatty acids or their salts. To some extent, these products guarantee good protection as long as the corrosion relates merely to an attack by condensation moisture or to corrosion due to salt-free ground Water. To combat the attacks by salt-containing, in particular, chloride-containing solutions, the previously known fuel oil additives offer a sufiicient protection only when disproportionately higher, frequently no longer economical, concentrations are employed.

Objects of the invention The object of the invention is to discover corrosion preventatives, in particular, corrosion inhibiting additives for fuel oils which guarantee, even in the presence of saltcontaining, especially chloride-containing water, an especially pronounced protection already with the use of small amounts of the additives.

Another object of the invention is the obtention of a corrosion inhibitor composition for fuel oils consisting of a mixture of:

(A) salts of aliphatic carboxylic acids having from 6 to 12 carbon atoms, with alkylamines substituted with hydroxyl groups; and

(B) salts of aliphatic carboxylic acids having from 4 to 12 carbon atoms, with alkylamines having from 4 to 16 carbon atoms, with the proviso that the total number of carbon atoms in said salt is more than 10;

said salts being present in said mixture in a ratio of 1:9 to 9:1 parts by weight.

A further object of the invention is the obtention of a corrosion preventative fuel oil containing from to 1000 parts per million of the aforesaid corrosion inhibitor composition.

These and other objects of the invention will become more apparent as the description thereof proceeds.

Description of the invention The invention accomplishes these objectives in that as corrosion preventatives, in particular corrosion in hibiting additives for fuel oils, such products are utilized which contain mixtures of:

(A) salts of aliphatic carboxylic acids having from 6 to 12 carbon atoms, with alkylamines substituted by bydroxyl groups; and

(B) salts of aliphatic carboxylic acids having from 4 to 12 carbon atoms, with alkylamines having from 4 to 16 carbon atoms, with the proviso that the total number of carbon atoms in said salt is more than 10;

said salts being present in said mixture in a ratio of 1 to 9 to 9 to 1.

In the case wherein salt A, carboxylic acids with 8 to 10 carbon atoms were used for the salt formation, a distinct improvement could be noted as compared with the shorter or longer chain acids. The use of carboxylic acids having from 6 to 10 carbon atoms as salt B can also be observed as an improvement compared with the shorter or longer chain acids. Among the amine components of the salt B, those having from 4 to 12 carbon atoms have the most favorable effect on the corrosion-preventing behavior. A further influence of the effectiveness of the salt mixture is possible by varying the proportions of the salts A and B in the total mixture. Here it became evident that the best results are obtained when the ratio of salt A to salt B fluctuates within the limits of 3:7 to 7:3 parts by weight.

Particularly effective mixtures are obtained when all improving factors are considered simultaneously. These preferred corrosion inhibitor compositions for fuel oils consist of a mixture of:

(A) salts of aliphatic carboxylic acids having from 8 to 10 carbon atoms, with alkylamines substituted by hydroxyl groups; and

(B) salts of aliphatic carboxylic acids having from 6 to 10 carbon atoms with alkylamines having from 4 to 12 carbon atoms, with the proviso that the total number of the carbon atoms in said salts is more than 10;

said salts being present in said mixture in a ratio of 3:7 to 7:3 parts by weight.

Suitable as acid components of the salt A are aliphatic carboxylic acids of natural origin, such as caproic acid, enanthic acid, caprylic acid, pelargonic acid, capric acid, undecanoic acid, lauric acid, and undecylenoic acid, and also synthetic carboxylic acids, as obtained by the paraffin oxidation or by addition of carbon monoxide and water to olefins. Generally, the above acids are alkanoic 3 acids and alkenoic aclds having 6 to 12 carbon atoms. The best efiectiveness may be attributed to the salts of caprylic, pelargonic and capric acids, of which caprylic acid (noctanoic acid) is most outstanding.

4 octylamine, decylamine, and dodecylamine proved of better suitability. The best results were obtained with dodecylamine.

A mixture of triethanolamine-caprylate and dodecyl- The alkylamine component substituted by hydroxyl 5 amine-caprylate has been found the most favorable comgroups of the salt A can consist of monoethanolamine, dibination of all of the possibilities, absolutely suitable and ethanolamine, triethanolamine, propanolamine, isoprofurnishing very satisfoctory results. Furthermore, this panolamine, triisopropanolamine, ethyleneoxide addition combination is the most effective when the mixture comproducts of amines or alk'anolamines, as for example, ponents are used at aratio of 1:1. butylamine+3 ethylene oxide units, n-hexylamine+6 10 The concentrations for use of the corrosion inhibitor salt ethylene oxide units, 2-ethyl-hexylamine-l-6 ethylene oxmixtures of the invention, required for a sufiicient proide units, octylamine+8 ethylene oxide units, dodecyltection in fuel oil, lies between 50 and 1000 p.p.m., based amine-{-12 ethylene oxide units, triethanolamine+2 on fuel oil. Preferably, amounts of 100 to 250 p.p.m., ethylene oxide units, triethanolamine+6 ethylene oxide based on fuel oil, are used. units, etc. The preferred alkylamine components of salt The tests and the test results presented in the following A are alkylamines containing hydroxyl groups of the serve for better comprehension of the objects of the informula vention. It is to be understood, however, that these em- Rz bodiments are not to be deemed limitative in any respect.

R1--l IRa Examples wherein R R and R are members selected from the For the investigation of the effectiveness of the corrogroup consisting of (a) hydrogen, (b) alkyl having from 1 sion preventative compositions, rust-free, polished and dcto 12 carbon atoms (0) hydroxyalkyl having from 2 to 6 greased steel plates of the quality ST 37-2 (-DIN 17.100), carbon atoms, and (d) -(CH CH -O:),,H, where n 1s 2 mm. thick, 20 mm. wide and 100 mm. long, were placed an integer of from 2 to 20, with the prov1so that at least in a standing cylinder of about 25 mm. diameter and 240 one of R R and R is selected from members (c) and mm. height. Then ml. of a pure unmixed fuel oil, to (d) above. Triethanolamine was found to be the most sultwhich various corrosion inhibitor salt mixtures had been able component. added, and 3 ml. of an aqueous 0.3% sodium chloride so- AS d components of the Salt 1 h y Valerie lution were added. The steel plates were submerged about acid as well as those acids already indicated as acid com- 30 6 mm. in the aqueous solution and were covered with oil ponents f the salts A can be used, of which ap a gi, up to a height of mm. In this way, the rust development nanthic acid, caprylic acid, pelargomc acid and caprlc could be observed on all three boundary phases: wateracid seem to be especially appropriate. Generally the steel, oil-steel and air-steel. The cylinders were kept locked above acides are alkanoic acids and alkeno1c acids having M fo 7 days in th d rk, Th aft th corrosion was 4 to 12 carbon atoms. The very best results are obtained judged visually nd i dica d i h th numbers 0 to 1() with caprylic acid. The individual values were assigned the following signi- As alkylamine components of salt B, butylamlne, hexylfi a amine, octylamine, decylamine, dodecylamine, hexadecylamine as well as amine mixtures as obtained, for example, 0 und?anged appparance 40 13=sl1ghtcorros1on from acids of corresponding chaln length as occurring 46=pronounced corrosion in natural o1ls and fats can be used. Preferably, these distinct corrosion are mono-alkylamines having from 4 to 16 carbon atoms. T ry Of the amines mentioned, those with short or medium The following table indicates the type of individual addilength chains, as for example, butylamine, hexylamine, tions, the amounts of these, as well as the evaluation.

TABLE I.-ADDITION [p.p.m. based on fuel 0111 Amount Example p.p.m. Salt A p.p.m. Salt B 01 corrosion 0 No addition 0 No addition 10 258 Triethanolamine-eaproate. 25g 5 2 125 'TriethanoIamine-eaproat 125 1 250 Triethanolamine-eaprylate. 0 3 125 do 125 0 250 Trlethanolamine-eaprate 0 4 125 -do 125 0 250 Triethanolamtnedeurate. 0 5 125 do 125 1 250 Monoethanolamine-caprylate. 0 5 125 -do 125 1 250 Tiiiigopropanolamine-cspry- 0 15 B e. 125 do 125 1 250 2-ethyl-hexyl-amine+fi 0 8 ethylene oxide unitseaprylete. 125 do 125 1 250 Dodecylamine+12 ethylene 0 g oxide units-eaprylate. 125 -do 125 Dodecylamine-eaprylate 1 0 250 Butylamine-caprylate. 4 12(51 Triethanolamine apryla do 1 'rartarsaisaaarrseiae o 3 0 250 Decylamine-eaprylate. 2 125 Triethanolamlne-eaprylate.. 125 do 0 0 250 Cocoamine-caprylate 2 125 Triethanolamine-eaprylate 125 0 0 250 Hexadecylamine-caprylate- 5 125 Triethanolamine-eaprylate.. 125 do 2 0 250 Dodecylamiue-butyrate 3 123 Triethanolamine-caprylate d0 1 111 55185131151551 125 3 0 250 2 34 125 Triethauolamine-caprylate- 125 0 35.--. 0 250 3 See fobtnotes at end of table.

TABLE I.Oontinued Ip.p.m. based on fuel oil] Amount Example p.p.m. Salt A p.p.m. Salt B oi corrosion 12g Trlethanolamine-caprylate. 2 125 Triethanolamine-caprylate 125 1 50 50 1 25 do 25 2 25 Triethanolamine caproate. 225 2 225 25 4 150 100 2 100 150 2 50 450 1 l Cocoarnine is the mixed amine derived from coconut oil fatty acids.

As it can be concluded from the preceding Table I, the individual salts already reduce the corrosive effect of the aqueous phase in the fuel oil to a certain degree when used by themselves. (See Examples 2, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25 27, 29, 31, 33, 35 and 37.) However, if the corrosion inhibitor mixtures of the invention are used, a substantially greater protection is obtained than that which was to be expected from the total of the individual effects of the two components of the mixture. This synergistic effect makes it possible to obtain a fully satisfactory corrosion protective effect against aqueous, chloride-containing solutions with low concentrations of use of the corrosion inhibitor compositions of the invention.

To gain further information concerning the efiectivenique. Moreover, with the use of the corrosion preventative compositions of the invention, no foreign substances which could have an unfavorable effect during the combustion of the fuel oil in the boiler are added to the fuel oil.

The preceding specific embodiments are illustrative of the invention. It is to be understood, however, that other expedients known to those skilled in the art can be employed without departing from the spirit of the invention or the scope of the appended claims.

We claim:

1. An aqueous sodium chloride corrosion inhibitor composition for fuel oils consisting of a mixture of (A) salts of aliphatic carboxylic acids containing from 8 to 10 carbon atoms selected from the group ness of the fuel oil additives of the invention, a quanticonsisting of alkanoic acids and alkenoic acids, with tative test was conducted according to the specifications alkylamines containing hydroxyl groups of the given by the Eidgenossischen Metallpriifungs und formula Versuchsanstalt (Federal Metal Testing and Research R1 Institute) (EMPA-Publications 2/ 1964).

A square, rust-free, polished, degreased steel plate (ST RPN-R DIN Of known weight and 2 mm. thickwherein R R and R are members selected from ness with a length of 20 mm, was placed in a 50 ml. the group consisting of (a) hydrogen, (b) alkyl beaker. ml. of fuel oil was poured over the steel plate, having from 1 to 12 carbon atoms, (c) hydroxyalkyl and while vigorously stirring, 0.23 ml. of water or 0.23 having from 2 to 6 carbon atoms, and (d) ml. of sodium chloride solutions having a concentration 40 varying from 0.3% to 3% were added. The aqueous (CHz CH2 'O)n H phase settled gradually in drops on the steel plate and Where n is an integer from 2 to 20, with the proviso produced a corresponding corrosion. The beakers, that at least one of R R and R is selected from covered with a watch glass, were allowed to stand in the members (c) and (d) above; and dark for 28 days. Thereafter, the rust formed was care- (B) Salts of aliphatic carboxylic acids containing fully scraped off with cellulose and the steel plate was again from 6 to 10 carbon atoms selected from the group weighed after having been dried. The loss of iron was consisting of alkanoic acids and alkenoic acids, with ascertained from the difference and converted into gram monoalkylamines having from 4 to 12 carbon atoms, of loss of iron/rn. of surface. The values thus obtained with the proviso that the total number of carbon are reported in the following table. atoms in said salt is more than 10;

TABLE II Triethanol- Dodecyl- G. of iron loss/m. of surface amuleamme- 1 solution FSEElZ ZhB 9355??? H20 NRC fuel oil) fuel oil) 0.3% 1. 0% 3. 0%

From the figures indicated in Table II, the outstanding corrosion inhibiting effect of the triethanolarninecaprylate/dodecylamine-caprylate mixtures can be seen even in the presence of greater sodium chloride concentrations which might be present in the ground water. These inhibiting effects occur even at extremely low concentrations of the corrosion inhibitor compositions of the invention in fuel oil.

The advantage obtainable according to the invention consists in that with even low concentrations of the indicated salt mixtures in fuel oil, a complete protection can be obtained for the storage tank against corrosion due to salt-containing water. Particularly, the salt-containing waters have until now caused the greatest difficulties with respect to the corrosion preventative techsaid salts being present in said mixture in a ratio of 3:7 to 7:3 parts by weight.

2. The aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 1, wherein the carboxylic acid component of the salt A is an alkanoic acid having 8 to 10 carbon atoms.

3. The aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 1, wherein the carboxylic acid component of the salt B is an alkanoic acid having 6 to 10 carbon atoms.

4. The aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 1 wherein the carboxylic acid component of salt A is caprylic acid.

5. The aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 1 wherein the alkylamine containing hydroxyl group component of salt A is triethanolamine.

6. The aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 1 wherein the carboxylic acid component of salt B is caprylic acid.

7. The aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 1 wherein the monoalkylamine component of salt B is dodecylamine.

8. The aqueous sodium chloride corrosion inihibitor composition for fuel oils of claim 1 wherein salt A is triethanolamine-caprylate, salt B is dodecylamine-caprylate and said salts A and B are present in a ratio of 1 to 1 parts by weight.

9. Fuel oil containing from 50 to 1000 parts per million, based on the fuel oil of the aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 1.

10. Fuel oil containing from 50 to 1000 parts per million, based on the fuel oil of the aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 8.

11. Fuel oil containing from 100 to 250 parts per million, based on the fuel oil of the aqueous sodium chloride corrosion inhibitor composition for fuel oils of claim 1.

References Cited UNITED STATES PATENTS 1,990,365 2/1935 Beale 4466 XR 2,382,818 8/1945 Rhodes et al. 252-392 XR 2,433,243 12/1947 Smith et al. 4466 2,587,546 2/ 1952 Matuszak 252392 XR 2,614,980 10/1952 Lytle 252392 XR 2,736,658 2/1956 Pfohl et al. 4466 XR 2,798,045 7/1957 Buck et al. 4471 XR 2,939,842 6/1960 Thompson 44-71 XR DANIEL E. WYMAN, Primary Examiner.

WILLIAM J. SHINE, Assistant Examiner.

US. Cl. X.R. 44-71 

